1. Field of the Invention
The present invention relates to a parking brake apparatus which operates a brake portion of a vehicle through manual operation when the vehicle is parked.
2. Description of the Related Art
In a parking brake apparatus for a vehicle, a brake operation lever protruding from a vehicle floor is operated to be moved rotationally so as to transmit a braking force to a brake portion (a brake main body) of the vehicle according to a rotated position of the brake operation lever. A proximal portion end of the brake operation lever is connected to the brake portion of the vehicle via a cable, and a rotated position of the brake operation lever can be locked by means of a locking mechanism. In addition, the locking mechanism is constantly biased in a locking direction with a spring, and when releasing a lock of the locking mechanism, a release operation knob at a distal end of the brake operation lever is made to be operated against a biasing force of the spring.
There is such a type of parking brake apparatus in which a driver is places a hand over a distal portion of a brake operation lever so as to cover the distal portion from above, and pushes a release operation knob in with a finger tip in a direction orthogonal to an axis of the brake operation lever (see Japanese Patent Unexamined Publication JP-A-2004-203276).
In this parking brake apparatus, a locking mechanism includes an engaging portion of a sector gear-like shape that is fixedly placed on a vehicle body side, and a locking pawl that is swingably supported at a proximal portion end of the brake operation lever and is engageable with the engaging portion at a distal end portion of thereof. The locking pawl is constantly biased in a direction in which the locking pawl is brought into engagement with the engaging portion with a biasing spring. In addition, an interlocking lever is held on the brake operation lever in such a manner as to move back and forth along an axial direction of the brake operation lever, and a distal end portion of the interlocking lever is interlockably engaged with the locking pawl. Further, a tapered cam surface, which comes into contact with a proximal end portion of the interlocking lever, is formed on a side wall of the release operation knob located inside the brake operation lever. Via the cam surface, a push-in operation force of the release operation knob is transmitted to the interlocking lever.
In this parking brake apparatus having the configuration described above, when the release operation knob is operated to be pushed in from a side of the distal end portion of the brake operation lever, the operation force so applied is transmitted to the locking pawl via the interlocking lever for the locking pawl to be disengaged from the engaging portion, whereby the rotation locking of the brake operation lever is released. Consequently, the driver can operate the brake portion of the vehicle by rotating the brake operation lever in such state.
However, in this parking brake apparatus, since the back and forth movement of the release operation knob in a direction orthogonal to the axis of the brake operation lever is converted into the back and forth movement of the interlocking lever which is substantially orthogonal to that of the release operation knob via a cam mechanism (the cam surface), there is a great friction loss in the cam mechanism, leading to a problem of a low transmission efficiency of operation force.